The present invention relates to a method for removing at least one flat article at a time from the bottom of a verticle stack.
When packaging stackable, flat articles, particularly very fragile or otherwise easily destroyed articles, such as cookies, crackers, sandwiches or the like, the articles are often collected in vertical stacks or horizontal rows. Since the assembly of these stacks or rows occurs irregularly over the entire width of the conveying line, this arrangement can be used to form an intermediate store from which at the end of these stacks or rows a certain number of articles can be removed in a periodic manner and formed into a packable stack which always contains the same number of articles.
The removal of the articles from the stacks or rows is difficult, due to their fragile nature and, accordingly, various devices have become developed for removing such articles from stacks or rows without damage.
German Pat. No. 1,045,892 discloses an apparatus for forming packagable stacks of the above-listed type of articles. The articles are here collected, for example, in three stacks. By means of a chain converyor equipped with grippers, the lower-most article in each group is pushed away and, after having slid over a suitable slide into compartments, is stacked between two guides. The guides support the rest of the stack while the lowermost article is pushed away, i.e. the pressure of the stack on the supporting surface of the guides must not exceed a certain level because otherwise the danger of breakage becomes too great. Therefore, the articles must rest on top of one another only throughout part of the stack. The curve in the stack required for this purpose, however, may have several inherent drawbacks.
In order to make the pressure on the lowermost article independent of the height of the stack, it has been proposed to periodically hold or release at least a group of the lower-most articles by means of a clamping device to thus maintain the friction due to pressure at always the same level during removal of the lowermost article. Such an arrangement is disclosed, for example in German Auslegeschrift [published patent application] No. 2,539,776. One wall of a shaft is made movable back and forth to periodically support and release the stack. To reduce the danger of breakage, the walls of the shaft are provided with an elastic coating.
Although with such a clamping wall it is possible to equalize tolerance-caused deviations in the dimensions of the articles, this movable shaft wall presents a time disadvantage in that a certain path has to first be traversed before the articles are released by the elastic coating. Moreover, multilayer articles could be transported vertically downwardly only if the outermost layers were connected together and not just resting loosely on one another, as this is the case, for example, with sandwiches.